Separation of ore particles preferentially coated with liquid fluorescent material



Dec. 5, 1967 T. c. MATHEWS 3, SEPARATION OF ORE PARTICLES PREFERENTIALLYCOATED WITH LIQUID FLUORESCENT MATERIAL Filed Dec. 7, 1964 O 4=9e9coeaaavw @O INVENTOR. 750 CI M4 Iva 5W5 United States Patent 3,356,211SEPARATION OF ORE PARTICLES PREFEREN- TIALLY COATED WITH LIQUID FLUORES-CENT MATERIAL Ted C. Mathews, P.0. Box 2061, Fairbanks, Alaska 99701Filed Dec. 7, 1964, Ser. No. 416,293 7 Claims. (Cl. 209-9) ABSTRACT OFTHE DISCLOSURE The patent describes a method for the concentration ofore by subjecting a quantity of crushed ore containing various types ofminerals to electromagnetic radiation to cause at least a portionthereof to fluoroesce at a characteristic wavelength distinct from thatof the rest of the ore mass, and sensing the characteristic wavelengthemitted by the radiated particles. The fluorescence of at least oneportion of the ore at characteristic wavelength distinct from that ofthe rest of the ore is achieved by the preferential coating of some ofthe ore particles with a liquid fluorescent material.

A common condition in many mining operations requires the mining oflarge quantities of worthless rock and the like to permit the recoveryof the valuable mineral portion. The mill must then crush, grind andtreat all of this material to extract the desired mineral.

To reduce the mill load it is desirable to reject at the mine theworthless material. In the instance where strong visual contrast existsbetween the mineral and the worthless portion, the mineral is oftenpicked by hand to up grade the feed for the subsequent crushing andgrinding operations. Heretofore, it has also been proposed toautomatically separate the mineral from the worthless portion by meanswhich detect the difference in the natural color or radioactivity of themineral and the worthless portion. However, these techniques havelimited utility since at many mines visual or radioactive contrast doesnot exist and hence, these ores may not be treated economically in thisway.

According to the present invention, it has now been found that thedesired mineral may be separated from the worthless portion by radiatingthe ore to cause a portion of it to emit at a characteristic wavelengthand sensing the emitted rays. The sensed rays are used to operate meansfor separating the ore into a desired and an undesired portion. In apreferred embodiment, it has been found that the desired separation maybe achieved by first treating a quantity of the ore with a liquid whichpreferentially coats the particles of one of the portions of the ore andis also capable of emitting at a characteristic wavelength upon exposureto ultraviolet light, X-rays, or other suitable type of electromagneticradiation. The treated ore is then passed to a separation zone where anelectromagnetic wave means sensitive to the characteristic wavelengthdetects which particles are coated and which particles are not. Thesensing means then functions to actuate a deflecting means whichphysically removes the coated particles from the body of ore particles.Thus, a desired or undesired type of mineral may be removed from themass of ore.

3,356,2ll Patented Dec. 5, 1967 It is an object of this invention toprovide a method for the treatment and concentration of ores.

It is another object of this invention to provide a process ofpreferentially coating one portion of a mass of ore-bearing rock with aliquid material which, when excited by exposure to electromagneticradiation, emits radiation of a wavelength distinct from that of therest of the mass.

It is another object of this invention to pass radiated Ore through azone where the radiation emitted by the particles is received in anelectromagnetic wave-sensitive element and certain of the radiatedparticles are automatically rejected in accordance with the selectiveresponse of the electromagnetic wave-sensitive element to thecharacteristic emissions therefrom.

These and other objects of this invention will become apparent from thedetailed description which follows.

According to this invention, a portion of a body of ore is caused toemit a characteristic wavelength, which wavelength is unlike thatemitted by the rest of the ore. The ore particles are then separatedaccording to whether they emit the characeristic wavelength. This ispreferably accomplished in the following manner. A quantity of orecontaining at least one valuable mineral portion is first treated with aliquid which preferentially coats the particles of one of the mineralsin the ore. The coating liquid, in adition to being specific toparticles of one of the minerals in the ore, is also capable offluoroescing at a characteristic Wavelength after exposure toultraviolet, X-rays, or any other suitable type of radiation. For thisreason, the coating liquid is sometimes referred to as the fiuoroscentmaterial. I

The radiation and separation of the ore will be better understood byreference to the accompanying schematic drawing depicting these aspectsof the process of this invention. The ore, which in the preferredembodiment has been treated with the fluorescent material to provideboth coated and uncoated particles, is placed on a conveyor 1 and causedto drop from the end of conveyor in a downward path past a radiationsource 2, into a zone where the characteristic radiation emitted by theradiated particles is received in an electromagnetic wave-sensing means3. The wave energy received by means 3 produces a small current which isamplified by an amplifier 4. The output of the amplifier then triggers arectifier switch 5 which, in turn, energizes deflecting means 6,normally a solenoidoperated air jet, water jet, or mechanical gate. Thedeflecting means knocks the particle emitting at the characteristicwavelength out of the stream of ore particles. These particles arereceived in collector 7, with the balance of the particles falling intocollector 8.

While in the preferred method, a portion of the ore particles ispreferentially coated to provide the characteristic emissions uponexcitation, the coating may be dispensed with in the case of naturaliluorescing ores. These ores, upon excitation, emit at a characteristicwavelength which can be used to activate separation. Typical materialsthat can be recovered from ore mixtures without coating or otherpretreatment are willemite, hydrozincite, uranite, calcite and sheelite.Other ores separated by the technique of this invention are firstpretreated to provide a preferential coating capable of emitting at acharactersitic wavelength upon exposure to one of the many forms ofelectromagnetic radiation.

In this specification, the ore particles which emit at a characteristicwavelength upon excitation will sometimes be referred to as beingfluorescent. Likewise, the coating materials used in many cases toprovide this property will be referred to as fluorescent materials. In anarrow sense, fluorescence refers to the property of absorbing radiationat one particular Wavelength and re-emitting it as light of a differentwavelength so long as the stimulus is active. However, I intend byfluorescence to indicate that property of absorbing radiation at oneparticular wavelength and re-emitting it as a different wavelength,whether or not visible, during exposure to the active stimulus, or afterexposure, or during both of these time periods. Thus, fluorescence isused generically herein to include the limited definitions of bothfluorescence and phosphorescence, and envisions the emission of acharacteristic wavelength whether or not visible.

In the preferred process, a wire variety of organic materials whichfiuoresce at a characteristic wavelength upon excitation by ultravioletlight, X-rays, or other radiation may be used to preferentially coateither the desired or the undesired portion of the ore. Illustrative ofthese organic fluorescent substances are anthracene, fluorescein,chrysene, aminoacetal picrate, petroleum base lubricating oil,allylamine picrate, aluminum palmitate, ammonium mandelate, calciumtriethanolamine theobroinine, ferrous stearate, glyceryl monooleate,glyceryl monostearate, hydrastine, hydrastine chloride, leadnaphthenate, lead linoleate, lead stearate, manganous stearate andbenzene. Certain of these materials are solids at ordinary temperaturesand hence are used in solution. For example, anthracene may be dissolvedin benzene.

To assist in adhering the fluorescent substances to the particles to becoated, there may be optionally employed any one of a number of bondingagents, hereinafter referred to as collectors. The collectors areusually long chain molecules with an atomic group which orients on theparticle surface and another group which orients on the fluorescentsubstance. While not bound by any theory, it is believed that thecollector is preferentially absorbed on the mineral surface anddisplaces the water film normally present thereon.

Collectors may be of any one of several types and are generallyclassified on the basis of their surface attachment into threegroups-anionic, cationic and neutral. Anionic collectors usch asxanthates adhere to minerals with a positive surface potential such asmetals and sulfides. Cationic collectors usch as amines adhere tosurfaces having a negative charge such as silicates. The neutralcollectors such as petroleum derivatives adhere to surfaces morepositive than the neutral hydrocarbon.

As has been already indicated, the use of a collector is not alwaysrequire-d. For example, many petroleum base lubricating oils will bothpreferentially adhere to certain minerals and also fluoresce whenexcited by electromagnetic radiation. The following list is merelyillustrative of some of the anionic collectors which may be employed inthis invention: the alkali alkyl xanthates, such as sodium sec-butylxanthate, potassium ethyl xanthate, sodium ethyl xanthate and potassiumamyl xanthate; aryl dithiophosphoric acids such as phenyldithiophosphoric acid; fatty acids such as stearic acid; thiocarbanilide; saponified fatty acids such as sodium stearate andpotassium stearate; sulfonated oils; glycerides such as tripalmitin andtristearin; and alcohols.

The cationic collectors include the alkyl ammonium halides such as amyltrimethyl ammonium bromide and cetyl trimethyl ammonium bromide; thealkali metal and alkaline earth metal alkyl aryl sulfonates such assodium dodecyl benzene sulfonate and calcium dodecyl benzene sulfonate;the alkyl ammonium acetates such as dodecylammonium acetate; long-chainalcohols such as dodecyl alcohol; ethylenically unsaturatedmonocarboxylic acids and their soaps such as oleic acid, linoleic acid,sodium oleate and sodium linoleate; fatty amine acetates; and benzene.

The fluorescent material and the collector, if present, may be appliedto the ore in a variety of ways, including spraying and dipping. Inpractice, the fluorescent material is added to the collector prior toore treatment. However, the ore may be treated with the collector andthe fluorescent material sequentially. Any excess of the fluorescentmaterial or collector may be readily removed by washing with water.

A fluorescent ore, or the fluorescent material preferentially absorbedon some of the ore particles can be caused to fluoresce at acharacteristic wavelength by radiation from the full spectrum ofelectromagnetic energy, varying from radio waves through infrared,visible, ultraviolet, gamma rays, and ionic bombardment. The specifictype of radiation employed in any given situation will depend upon theparticular fluorescent material being used. For example, anthracene andpetroleum base lubricating oils upon exposure to ultraviolet light(25003700 angstroms) will fluoresce strongly at about 4000 angstroms.

By appropriately selecting the fluorescent material and collector, it ispossible to coat almost any mineral in preference to any other materialpresent. Thus, by my invention, any ore portion, whether naturallyfluorescent or not, may be readily separated from any other portion. Itwill, therefore, be recognized that the following examples are presentedsolely to illustrate the invention and should not be regarded aslimitative in any way.

Example I A quantity of crushed ore containing primarily quartz andcalcite is coated with a petroleum base lubricating oil (sold by theStandard Oil Co. under the name Penn Motor Oil SAE 30). The excesslubricating oil is removed by flushing with water. Microscopicexamination of the particles reveals that the quartz rejects thelubricating oil while coating the calcite. The apparatus used toseparate the ore includes a conveyor having an ultraviolet light sourcestationed at its discharge end. Below the ultraviolet source ispositioned a 931-A photo multiplier tube sensitive to 4000 A. emissions.A Wratten filter is interposed in the optical path of the tube toeliminate stray ultraviolet. The output of the tube leads to anamplifier which triggers a silicon controlled rectifier switch which, inturn, energizes a solenoid-operated air jet located below theultraviolet source. The treated ore is placed on the moving conveyorbelt at a rate which provides a single layer of ore particles. The oreparticles are exposed to ultraviolet light as they leave the end of theconveyor and'are in free fall. The 4000 A. emissions from the coatedparticles are sensed by the photo multiplier tube. It is found that theair jet deflector actuated by the tube produces a high degree ofseparation of the coated calcite from the quartz.

Example II A quantity of crushed ore containing quartz, sandstone,argillite, schist, quartzite and calcite is first washed to removeadhered particles. The ore is then sprayed with an aqueous mixture ofdodecylammonium acetate and anthracene dissolved in benzene. The ore isthen washed with water to remove the coating solution from the unwantedportions and to leave a coating of anthracene only on the quartzparticles. The quartz is then separated from the rest of the oreaccording to the procedure and employing the apparatus described inExample I.

Example III A quantity of crushed ore containing sulfide minerals,sandstone, argillite, schist and calcite are washed with water to removeadhered particles. The ore is then washed with an aqueous solution ofanthracene and phenyl dithiophosphoric acid. The excess is removed bywashing with water. It is found that the anthracene preferentiallyadheres to the surface of the sulfide minerals. The sulfide mineral isthen effectively separated from the bulk of the ore in the manner setforth in Example I.

In the practice of the process of this invention, separations of 90% ofefficiency have been achieved, using a variety of ores including thefollowing:

Quartz from Quartzite Sandstone Argillite Calcite Mica schist Calcareousschist Hornblend schist Limestone from- Quartz Sandstone ArgilliteCalcite Mica schist Calcareous schist Hornblend schist As can be seenfrom the foregoing, the process of this invention is particularly wellsuited to the concentration of quartz, calcite and limestone-containingores.

The wave sensing means 3 is typically a photo multiplier tube having asensitivity to specific wavelength bands. The bands received at thesensing means are narrowed, as required, by the use of filters. Tubesare cornmercially available having sensitivities from the infrared tothe ultraviolet. Thus, it is a simple matter to select a tube which issensitive to the characteristic wavelength emitted upon electromagneticexcitation of any given fluorescent ore or material.

In these photo multiplier tubes, photons which result from fluorescenceare received in a first stage and converted to electrons which aredeflected to succeeding states by electrostatic fields and multiplied bysecondary emission from each stage. The weak current emerging from thephoto multiplier tube may be amplified in a conventional solid stateamplifier. Since the current from the amplifier is used to operatedeflection means 6, it is usually necessary to incorporate an adjustabledelay network in the amplifier in order to achieve register between theposition of the particle at the time of detection by the sensing meansand the time of deflection.

Since the throughput of ore particles in the process of this inventionmust be as high as possible, the particles are passed before the sensingmeans at a high velocity. The sensing means is normally placed so thatthe ore particles passing before it are in free fall and thus have ahigh velocity and a fixed path.

As can be seen in the drawing, the sensing means is conveniently locatedso that the sensing means detects the particles soon after they leavethe end of the conveyor. To assure a high degree of separation, the oreparticles are fed to the conveyor at arate which provides a singlelayer. While only one sensing means is shown in the drawing, it will beunderstood that the number of sensing means used is dependent upon thetonnage of ore particles to be handled, the width of the conveyor, andthe size of the particles. The field of detection for each sensing meansis limited to an area approximately equal to the area of an individualore particle.

The particular deflecting means 6 chosen has been found to depend on theindividual size of the ore particles. An air jet is useful on sizesbelow /2 inch. A water jet is used on sizes between /2 inch and 4inches, while a mechanical gate is used for even larger sizes.

While the process of this invention has been described with particularreference to the separation of ore particles while in free fall from theend of a conveyor, it will be evident to anyone skilled in the art thatmy invention may be practiced in many other ways and with the aid ofmany different types of apparatus. For example, the particles may bemechanically separated while moving in any desired plane including thehorizontal. In the case of small batches, it may be expedient to performthe actual separation manually.

Having fully described the invention, it is intended that it be limitedonly by the lawful scope of the appended claims.

I claim:

1. The method for the concentration of ore which comprises treating aquantity of crushed ore containing various types of minerals with aliquid fluorescent material capable of preferentially coating some ofthe particles in the ore, radiating the treated quantity of ore toexcite the liquid on the coated particles to fluoresce at acharacteristic wavelength, and separating the coated particles from theuncoated particles on the basis of the difference in their emittedwavelengths.

2. The method for the concentration of ore which comprises treating aquantity of crushed ore containing various types of minerals with aliquid fluorescent material capable of preferentially coating some ofthe particles in the ore, radiating the treated quantity of ore toexcite the liquid on the coated particles, passing the radiated treatedquantity of ore through a zone where the characteristic wavelengthemitted by the radiated coated particles is received in anelectromagnetic wavesensitive element, and automatically displacing thecoated particles in accordance with the selective response of theelectromagnetic Wave-sensitive element to the characteristic wavelengthreceived therein.

3. The method for the concentration of calcite-containing ore whichcomprises treating a quantity of calcitecontaining ore containingvarious types of minerals with a liquid fluorescent material capable ofpreferentially coating some of the particles in the ore, radiating thetreated quantity of ore to excite the liquid on the coated particles,passing the radiated treated quantity of ore through a zone where thecharacteristic wavelength emitted by the radiated coated particles isreceived in an electromagnetic wave-sensitive element, and automaticallydisplacing the coated particles in accordance with the selectiveresponse of the electromagnetic wavesensitive element to thecharacteristic wavelength received therein.

4. The method for the concentration of quartz-containing ore whichcomprises treating a quantity of quartzcontaining ore containing varioustypes of minerals with a liquid fluorescent material capable ofpreferentially coating some of the particles in the ore, radiating thetreated quantity of ore to excite the liquid on the coated particles,passing the radiated treated quantity of ore through a zone where thecharacteristic wavelength emitted by the radiated coated particles isreceived in an electromagnetic wave-sensitive element, and automaticallydisplacing the coated particles in accordance with the selectiveresponse of the electromagnetic wave-sensitive element to thecharacteristic wavelength received therein.

5. The method for the concentration of sulfide-containing ore whichcomprises treating a quantity of sulfidecontaining ore containingvarious types of minerals with a liquid fluorescent material capable ofpreferentially coating some of the particles in the ore, radiating thetreated quantity of ore to excite the liquid on the coated particles,passing the radiated treated quantity of ore through a zone where thecharacteristic Wavelength emitted by the radiated coated particles isreceived in an electromagnetic wave-sensitive element, and automaticallydisplacing the coated particles in accordance with the selectiveresponse of the electromagnetic wavesensitive element to thecharacteristic wavelength received therein.

6. The method for the concentration of ore which comprises treating aquantity of ore containing various types of minerals with anthracene topreferentially coat some of the particles in the ore, radiating thetreated quantity of ore to cause the anthracene on the coated particlesto fiuoresce, passing the radiated treated quantity of ore through azone where the characteristic wavelength emitted by the radiated coatedparticles is received in an electromagnetic Wave-sensitive element, andautomatically displacing the coated particles in accordance with theselective response of the electromagnetic wavesensitive element to thecharacteristic wavelength received therein.

7. The method for the concentration of ore which comprises treating aquantity of ore containing various types of minerals with a petroleumbase lubricating oil to preferentially coat some of the particles in theore, radiating the treated quantity of ore to cause the lubricating oilon the coated particles to fiuoresce, passing the radiated treatedquantity of ore through a zone Where the characteristic wavelengthemitted by the radiated coated parti- 8 cles is received in anelectromagnetic wave-sensitive element, and automatically displacing thecoated particles in accordance with the selective response of theelectromagnetic wave-sensitive element to the characteristic wavelengthreceived therein.

References Cited UNITED STATES PATENTS 1,577,328 3/1926 Lewis 209 -1672,096,099 10/1937 Gaugler 250--71 2,267,999 12/19'41 Switzer 250-712,717,693 9/1955 Holmes 209-1115 2,878,392 3/1959 Polito 25071 3,011,63412/1961 Hutter 209111.5 X 3,016,143 1/1962 Trachta 209-167 X 3,061,72310/1962 Kaptf 250-71 3,118,060 1/1964 Klein 25071 3,255,881 6/1966Holderreed 209--164 X FRANK W. LUTTER, Primary Examiner.

1. THE METHOD FOR THE CONCENTRATION OF ORE WHICH COMPRISES TREATING A QUANTITY OF CRUSHED ORE CONTAINING VARIOUS TYPES OF MINERALS WITH A LIQUID FLOURSCENT MATERIAL CAPABLE OF PREFERNTIALLY COATING SOME OF THE PARTCLES IN THE ORE, RADIATING THE TREATED QUANTITY OF ORE TO 